Revolving sprinklers are widely used and very common for specific agricultural use as well as for wetting large areas, extinguishing fire, dish washers, etc. For the sake of simplicity, the background of the invention, as well as the description of the invention proper, will be described as they refer to the agricultural irrigation application. This should not be wrongly taken to imply that as meant to limit the current invention and the attending claims to be valid solely for the agricultural irrigation—which is used for clarity of the explanations and eliminating cumbersome additional examples.
Achieving an increase of the area covered by single sprinkler, would naturally reduce the quantity of equipment pieces needed for covering a given area, and thus lower equipment cost. A gained synergy effect is evident—the deployment of the equipment and its transfer to other areas is simpler and faster, as well as lowering current and special maintenance expenditures.
The need for- and yearning to- increase the effective distance unto which water is sprinkled by revolving sprinklers, resulted in producing slower revolving sprinklers whose water ejection jet patterns is slowed down, for example to 1-10 rpm.
As dictated by basic physics laws, the water flow exiting a revolving sprinkler is made of two velocity components—one in the tangential direction and the other in the radial one. Decreasing the rotation speed increases the component in the desired radial direction (while reducing the one in the tangential direction). Thus, decreasing the rotation speed results in a larger range—the radial component water jet gets sprinkled farther away.
Needless to say, that by reducing the rotation speeds an additional benefit will be gained—namely a decrease of the abrasion and wear of the sprinklers' dynamic components, which are given to increased wear at higher rotation speeds.
In the past, several mechanisms were employed in revolving sprinklers for reducing the rotation speed. A well-known example is the implementation of a slowing down mechanism based on a transmission of toothed wheels. Such a transmission is a relatively expensive one, as it requires many parts. These wheels are naturally sensitive and given to enhanced abrasion and wear, coupled with accumulation of dirt on them. Packing the toothed wheels in a sealed box, in order to prevent contact with the water (a contact that leads to accumulation of fur on them) and contact with other contaminating substances, leads to increased price. In any case it is not an adequate solution to the complexity of the system (profusion of parts and above-mentioned sensitivity to abrasion and wear).
Another example for slowing down mechanism is the implementation of a mechanism based on the resistance provided by viscous liquid (e.g., silicone oil), to movement of dynamic component items immersed in it. This resistance to movement is, in given geometrical conditions, proportional to the movement velocity of the immersed dynamic component. The braking force in the viscous liquid increases linearly with the movement velocity of the immersed dynamic component, so that at zero speed the viscous liquid exerts no resistance to movement, whereas at high speeds the viscous liquid exerts high braking resistance and slowing down of the immersed dynamic component. Outstanding advantages of the viscous damping mechanism are—the small number of parts implemented in its assembly; relying on relative movement between smooth surfaces located in close distance (with shearing forces evolved at their interface, within the viscous fluid) as compared to the abrasion and wear evolved in the case of the mechanical transmission, accompanies the locking up of the sprockets one in another; and a synergic additional advantage imparted by the viscous liquid that constitutes a lubricating agent preventing wear and abrasion.
The application of viscous damping mechanisms in revolving sprinklers is described, for example, in patents U.S. Pat. Nos. 3,415,258; 4,440,345; 4,932,590; U.S. RE 33,823 and U.S. Pat. No. 5,377,914.
In the structures described by above cited patents, the rotation velocity of the revolving sprinklers is dependent on the drive moment generated by the force of the water being ejected through a mouthpiece.
The above is correct whether one considers a sprinkler of the kind in which a water jet emerging from a static nozzle is thrown unto a stream deflecting component that rotates around a rotation axis (a “spinner” or a deflecting component—see for example the structures of the sprinklers described in patents U.S. Pat. No. 3,415,258 and U.S. RE 33,823), or a sprinkler in which there exists a rotateable turret that is installed with a mouthpiece or mouthpieces (at least one), from whose nozzle a water jet emerges, and it itself (the water jet) by the reaction force it generates, serves to generate a moment to drive the rotateable turret around a rotation axis (see for example patents U.S. Pat. Nos. 4,440,345 and 5,377,914).
Under the presented circumstances, just the change in throughput, namely passing from low throughput to high throughput and vice versa, varies the drive moment generated by the sprinkler. In any case, in the configurations of the sprinklers described in the above cited patents, the rotation velocity of the flowing water emerging from them would also be changed (combined with a variation of the water jetting range).
Worse than that, it was found that subjecting the viscous damping mechanism to varying driving moments, might cause, after a given time period, to a failure of the mechanism and to phenomena of free spin rather than controlled action of the rotating components (whether it will be the spinner or deflector upon which the water impacts, or the rotating nozzle from which the water emerges).
Another disadvantage found in some of the revolving sprinklers manufactured according to the above cited patents, is the absence of the ability to change the angle of the water emergence direction and suiting it to the needs of the farmer. For example, irrigating in an open area, requires at times a relative higher angle for achieving a maximal range. On the other hand, irrigating in a grove under the trees dictates the adaptation of a relative low elevation angle. Most of the sprinklers described by the above cited patents do not offer such a solution in any manner whatsoever akin to these example (see for example, patents number U.S. Pat. Nos. 3,415,258; 4,440,345; 4,932,590; U.S. RE 33,823).
An additional drawback is found, for example—in a mechanical structure based on a “bridge like” construction that forms a link between one end of the sprinkler to its other end (see for example said “bridge” structures described in cited patents U.S. RE 33,823 and U.S. Pat. No. 3,415,258). This “bridge” structure is located in the passage path of the revolving water jet. The collision of the water jet with the “bridge” clearly disrupts the flow and exposes the sprinkler structure to shocks and vibrations that harm its stability.
A further example of a drawback that will be found in several types of some sprinklers if manufactured by the methods given in above cited patents stems from the fact that the water jet has to “slam” on an intermediate component, a deflecting component that rotates around a rotation axis (spinner or deflector, see for example the structures of the sprinkles described in patents U.S. Pat. No. 3,415,258 and U.S. RE 33,823). Evidently, such a structure limits the range that would have been achieved by direct casting of the water jet stream through a nozzle.
One more drawback of those sprinklers is the absence of a solution for a problem associated with the blocking of a sprinkler's mouthpiece, except dismantling it and cleaning it separately. This is a familiar and non-relished maintenance chore known to every farmer and resulting, additionally, in extra labor and in long down periods of the sprinklers system.
Another drawback of the sprinklers being described, is the lack of a solution to the problem of water down flow (drain) from the water supply system's lines, through the sprinkler's body, after the sprinkling was completed and the main system valve at the head of the pipe line is closed. Closing the main valve of the water supply line feeding the revolving sprinkler results in loss of residual water left in the line and the sprinkler, by slowly oozing out of the line through the sprinkler's body. In addition, modem irrigation techniques calls for providing short irrigation pulses with short duration breaks between them, which means many time of opening and closing the main valve, loosing large quantities of expensive water and delays caused as the empty lines have to be refilled and pressure in the line brought up.
There are even more drawbacks to be found in the revolving sprinklers if they would be built in accordance with the methods offered by the patents that we kept quoting, and let us present just one more in conclusion—this is the absence of the “pop up” configuration in all the above (except for the revolving sprinklers built in accordance with patent U.S. Pat. No. 4.932,590—but also this one would not provide operational flexibility from the point of view water throughput quantities and the aspect of low angle water jet direction). The pop up structure is used for up-righting the rotating assembly from which the water is sprinkled, for operating above the surface when pressure builds up in the line, and for convergence of the system when the water pressure in the line diminishes.